Insights into the evolution of mycotoxin biosynthesis in the fungus Fusarium
R. H. PROCTOR (1), T. Lee (2), M. T. Amatulli (3), S. P. McCormick (3), D. W. Brown (3), M. Busman (3), C. Maragos (3), T. J. Ward (3). (1) USDA ARS MWA NCAUR, Peoria, IL, U.S.A.; (2) National Academy of Agricultural Science, Rural Development Administration, Suwon, Korea; (3) USDA ARS NCAUR, Peoria, IL, U.S.A.
Collectively species of <i>Fusarium </i>are pathogens of almost all economically important plants and produce over 50 families of secondary metabolites (SMs), including some of the mycotoxins (e.g. fumonisins and trichothecenes) of greatest concern to food/feed safety. In fungi, genes responsible for biosynthesis of an SM are usually located next to one another in a gene cluster. A typical biosynthetic gene cluster encodes enzymes that catalyze SM synthesis, a transport protein for SM secretion, and a regulatory protein that controls transcription of cluster genes. Comparative analyses of such clusters have provided insight into evolutionary processes responsible for variation in mycotoxin production in <i>Fusarium</i>. Presence and absence of a cluster is the primary cause of interspecies differences in ability versus inability to produce a mycotoxin. In some cases, this variation in ability has resulted from relatively recent horizontal transfer or loss of a cluster. In addition, intra- and inter-species differences in production of different analogues of a mycotoxin family can result from loss of a cluster gene or from variation in function of homologs of a gene. In contrast, some clusters exhibit marked variation in DNA sequences or gene organization without effects on mycotoxin production. Thus, SM gene clusters can be dynamic genetic elements, and this dynamism is responsible for qualitative differences in mycotoxin production within and among species of <i>Fusarium</i>.
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